The present invention relates to a collision detection device for a motor vehicle, in particular a passenger motor vehicle, for detecting a collision with a pedestrian, wherein the collision detection device has a pressure measurement chamber which is formed by a tube.
In a motor vehicle, in particular a two-track passenger motor vehicle, it is known to arrange between a bumper cover and a front bumper crossmember an energy-absorption element which, for the purpose of protecting a pedestrian, is deformable at a relatively low force level in the event of a collision of the motor vehicle with the pedestrian. A collision detection sensor system based on pressure measurement is also known. The collision detection sensor system serves for detecting a collision with a pedestrian, with the result that a control unit can actively direct passenger protection measures, for example the raising of a front flap or the triggering of a front windshield airbag, based on this detection. Such a collision detection sensor system has a tube to which there is connected a pressure sensor which is able to detect pressure variations within the tube. The tube is filled with air under atmospheric pressure. If the tube is deformed as a result of the collision with the pedestrian, this brings about a change in pressure in the interior of the tube. Such a tube is normally arranged in the transverse direction of the vehicle in abutment with the bumper crossmember and accommodated in a groove in the energy-absorption element.
Depending on the configuration of the bumper cover, the bumper crossmember and/or the energy-absorption element and also the tube, there is a requirement for improving a response behavior of the collision detection sensor system, that is to say for detecting the collision at an earlier point-in-time and for improving a strength of a detection signal.
It is the object of the present invention to provide a collision detection device for a motor vehicle for detecting a collision with a pedestrian, which device improves a response behavior and/or a sensitivity during the collision with the pedestrian in a low-cost manner by way of a simple measure.
This and other objects are achieved by a collision detection device for a motor vehicle, in particular for a motor vehicle front end or a motor vehicle rear end, for detecting a collision with a pedestrian, having a pressure measurement chamber which is formed by a tube, and having a flexurally rigid structural element, wherein the tube is formed and arranged so as to be deformable in a collision-induced manner and is supported against the structural element in a direction transverse to a vertical direction of the vehicle and in precisely one vertical direction of the vehicle.
The collision detection device according to the invention for a motor vehicle for detecting a collision with a pedestrian has a pressure measurement chamber which is formed by a tube, and has a flexurally rigid structural element. The tube is formed so as to be deformable in a collision-induced manner, that is to say as a result of a collision of the motor vehicle with the pedestrian, and is correspondingly arranged. Also, the tube is supported in one direction, in particular in precisely one direction, transverse to a vertical direction of the vehicle. Furthermore, the tube is substantially, in particular flexurally rigidly, supported against the structural element in precisely one, that is to say in exclusively one, vertical direction of the vehicle. “In precisely one vertical direction of the vehicle” means that the tube is supported either upwardly or downwardly, but is not supported in both of these directions.
The inventors have found that, in the event of a collision with a pedestrian, who normally has a center of gravity which is not located at a height of the tube (the center of gravity is normally located above a vehicle front end), the collision load on the vehicle front end acts obliquely in the direction of the flexurally rigid structural element. It is therefore advantageous if the tube is supported in a direction transverse to the vertical direction of the vehicle, and in precisely one vertical direction of the vehicle, such that both that component of the collision load which acts in the vertical direction of the vehicle and that component of the collision load which acts in the direction transverse to the vertical direction of the vehicle are able to deform the tube effectively. If the tube were supported in both vertical directions of the vehicle, that is to say upwardly and downwardly, that component of the collision load which acts in the vertical direction of the vehicle would be unable to deform the tube. Accordingly, by supporting the tube in precisely one vertical direction, it is possible for a collision load acting on the tube obliquely from below or obliquely from above to be detected better, that is to say more quickly and more sensitively.
The collision detection device is preferably arranged in a motor vehicle front end, but may also be arranged in a motor vehicle rear end.
“A direction transverse to a vertical direction of the vehicle” means in particular a direction perpendicular to or substantially perpendicular to a vertical direction of the vehicle. The direction transverse to the vertical direction of the vehicle is furthermore preferably substantially a longitudinal direction of the vehicle.
According to a preferred refinement of the present invention, the structural element has a first support surface which extends substantially parallel to the vertical direction of the vehicle, and has a second support surface which extends transversely to the vertical direction of the vehicle, for example substantially in a longitudinal direction of the vehicle.
The second support surface may be formed either on a top side or a bottom side of a projection which is connected to the first support surface or the structural element in a flexurally rigid manner or which is formed integrally with the first support surface or the structural element, and a lower side of the tube or an upper side of the tube may be supported against the projection. The term “projection” also covers a shoulder or a step.
The first support surface may in particular be formed behind the tube in the collision direction, and the second support surface may be formed below the tube.
In the case of a motor vehicle front end, this means that the first support surface is formed behind the tube in the main direction of travel of the vehicle.
The structural element may in this case be a crossmember element, in particular a bumper crossmember, and the first support surface may be formed on an outer side of the crossmember element, and the second support surface may be formed on a projection which is connected fixedly in terms of torque to the crossmember element or which is formed integrally with the crossmember element.
In the case of the front bumper crossmember, the first support surface is thus formed on a front side of the bumper crossmember.
According to an alternative advantageous refinement of the collision detection device, the first support surface may be formed in front of the tube in the collision direction, and the second support surface may be formed above the tube.
In particular, the structural element may be a vehicle outer skin, for example a bumper cover, and the first support surface may be formed on an inner side of the vehicle outer skin, and the second support surface may be formed on a projection which is connected fixedly in terms of torque to the vehicle outer skin.
According to a further advantageous refinement of the collision detection device, the second support surface may extend along an entire effective length of the tube.
Alternatively, it is also possible for the second support surface to extend sectionally along the effective length of the tube.
The effective length of the tube is that region of the tube which is provided for detecting the collision with the pedestrian.
This allows a target response behavior to be suitably adapted to the structural conditions of the motor vehicle.
According to a further preferred refinement of the present invention, in the collision detection device, the tube is surrounded at least partially by a plastically deformable energy-absorption element or is at least adjacent to the energy-absorption element, wherein the energy-absorption element is arranged in front of or behind the structural element in the collision direction.
This allows the oblique collision load to better deform the tube as a result of mutual supporting of the tube between the energy-absorption element and the structural element, with use made of the components of the collision load in a vertical direction and the direction transverse to the vertical direction. In other words, in the event of a collision, the tube is clamped obliquely between the energy-absorption element and the structural element by way of the obliquely acting collision load.
The energy-absorption element is for example a so-called pedestrian protection element, in particular a passive pedestrian protection element.
The energy-absorption element consists for example of a foam, in particular a thermoplastic foam, which, for the purpose of protecting pedestrians, is deformable at a relatively low force level.
The energy-absorption element is arranged for example between a vehicle outer skin and a crossmember.
The energy-absorption element may bear against the tube, or at least come into abutment with the tube in the event of a collision, on sides of the tube which are not supported, which are in particular not supported in a longitudinal direction of the vehicle and in a vertical direction of the vehicle. In other words, the tube is indirectly or directly supported against the energy-absorption element in the other, that is to say opposite, vertical direction of the vehicle, and the tube is indirectly or directly supported against the energy-absorption element in the opposite direction to the direction transverse to the vertical direction of the vehicle.
The tube preferably consists of an extruded plastic material, for example an elastomer material, in particular a silicone material. This material is inexpensive and permits an easily deformable tube.
The collision detection device also advantageously has a pressure sensor which is arranged such that it communicates with the pressure measurement chamber. The pressure sensor is adapted to detect a pressure and/or a change in pressure in the pressure measurement chamber as a result of the collision-induced deformation of the tube.
Here, “collision direction” identifies the direction in which the collision counterpart, that is to say the pedestrian, collides with the motor vehicle, that is to say the direction in which the collision counterpart exerts a collision force on the motor vehicle.
Above-mentioned refinements of the invention may be combined with one another in any desired manner where possible and expedient.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.
A detailed description of the exemplary embodiments of the present invention follows with reference to the figures.